The present invention relates to an optical circuit substrate comprising a substrate and optical fiber laid and fixed in the form of a circuit on the substrate.
Optical fiber is employed in communication which use light having a very high frequency as the carrier wave, and has advanced as a communication medium which enables a high quality transmission with a small loss over a long distance.
It has been proposed and developed in recent years to use the optical fiber, which has been developed thus for use in long distance communication, for transmission in a short distance communication or in an apparatus in place of electric wire, which permits transmission of only a relatively small amount of information.
For example, JP-A-61-186908 discloses, in the field of communication systems or instrumentation systems which operate by utilizing inter-transformation between light and electrons, a system in which three or more layers of substrates each provided with a driving circuit comprising an optical active element, an optical passive element and an optical active element are provided and optical circuits are provided between the substrates. With regard to optical fiber, there is described in the disclosure that an optical branching-coupling device 60 mm in length has been provided by using two lines of optical fiber with a spacing of 2 mm on a UV resin substrate.
JP-A-1-180505 discloses a method of forming an optical circuit wherein optical fiber is laid on a substrate through the medium of an adhesive layer. It is described therein that the optical fiber has been laid by using a laying tool on an acrylic adhesive layer formed on an ABS resin substrate.
JP-A-4-311905 discloses a circuit board in which a flexible base material having optical fiber interposed therein is sticked to a rigid substrate such that the flexible base material rises over the substrate from the intermediate part of the substrate so that the tip of the optical fiber can be connected to a connector.
Furthermore, as disclosed in JP-A-1-183605, there is known an optical circuit substrate which has on the end face of the substrate a condensing lens that receives aslant a light from the optical fiber.
When, as disclosed in JP-A-61-186908, in communication systems or instrumentation systems which operate by utilizing inter-transformation between light and electrons, three or more layers of substrates each provided with a driving circuit comprising an optical active element, an optical passive element and an optical active element are provided, and optical circuits are provided between the substrates, there arise disadvantages in that the thickness of the resulting substrate is unfavorably large and moreover, when a fault occurs in the optical circuit, the entire part of the substrate including the electron circuit has to be replaced, leading to an economical disadvantage.
In the above-mentioned method, furthermore, there is a large gap between the accuracy of alignment required for optical interconnection and the accuracy of actual electrical mounting of an optical element, etc., so that allowance for absorbing a considerable accuracy gap is necessary in the optical interconnection part. This leads to an increased size of the substrate and resultant disadvantage in practice.
From such a viewpoint, it is economically more advantageous to provide an optical circuit alone independently, as disclosed in JP-A-1-180505 and JP-A-4-311905.
However, when optical fiber is laid on an adhesive layer by means of a tool, as disclosed in JP-A-1-180505, the entire part of the optical fiber is fixed to the adhesive and, to take out signals from the optical circuit, it is necessary to peel off the necessary part or to take some means not to fix the necessary part, and the optical fiber which has not been fixed is apt to be broken.
Further, even when, as disclosed in JP-A-4-311905, a flexible base material having optical fiber interposed therein is sticked to a rigid substrate such that the flexible base material is raised over the substrate from the intermediate part of the rigid substrate (to assume a form of so-called xe2x80x9cpig tailxe2x80x9d) so that the tip of the optical fiber can be connected to a connector, there are problems in that the fiber which has not been fixed is similarly apt to be broken, that the optical fiber connected to the tip of the raised optical fiber needs an optical inter-connection part of increased size because the area of the member part is large and that the length of the fiber which is not fixed increases because a certain extent of movement is necessary at the time of operation of connecting a connector.
When a condensing lens which receives obliquely a light from optical fiber is provided at the end face of the substrate as disclosed in JP-A-1-183605, there arises a problem in that when the angle of inclination is decreased, the position of fixing the optical fiber has to be lowered, whereas when the angle is increased the height of the substrate has to be increased.
An object of the present invention is to provide an optical circuit substrate which permits the connection of the optical circuit with good accuracy and without occupying much space and a process for preparing such an optical circuit substrate with good efficiency.
The present invention provides an optical circuit substrate comprising an optical fiber placed and fixed in the form of a circuit on a surface of a substrate, wherein an end portion of the optical fiber is cut so as to have an angle which permits refraction or reflection of light most in the direction of 90 degrees relative to the substrate surface, and said substrate having a hole therethrough beneath the cut-section of the fiber, said hole having a metal film on the inner wall thereof, and a process for the preparation thereof.
The present invention also provides an optical circuit substrate comprising optical fibers placed and fixed in the form of a circuit on both surfaces of a substrate, wherein an end portion of the optical fiber is cut so as to have an angle which permits refraction or reflection of light most in the direction of approximately 90 degrees relative to the substrate surface, said substrate having holes therethrough beneath the cut-section of the fiber, and the cut-section of the optical fiber being provided on both surfaces of at least one of the holes, and a process for the preparation thereof.
The present invention further provides a process for the preparation of an optical circuit substrate, which comprises placing and fixing an optical fiber in the form of a circuit on a surface of a flexible base material, the optical fiber being provided so as to extend farther outside than the flexible base material, making an optical fiber fixed to another rigid substrate intersect with the optical fiber provided previously so as to extend farther outside than the flexible base material, and connecting the two fibers by applying a light-transmittable adhesive to the intersecting point of the fibers.
The present invention still further provides a process for the connection of optical circuits which comprises making two plastics-made optical fibers intersect with each other, and connecting the two fibers by applying pressure to the intersecting point of the fibers while applying energy by vibration to the point.